Imma say this: you are good in some ways, but you have room for improvement... for example: I often see you rushing towards your opponent with unwieldy approaching attacks, like fair and other things. You really should NEVER plan on approaching with fair unless you know for sure that you will get the opponent and they won't take advantage of your mishaps by DI'ing outwards. Fair, IMO, is a severely over-rated move. The only thing it serves a purpose for is a scare tactic... and spacing... it isn't good enough of an attack to do much of anything against one who is wiser. I saw you using fair as a retreated aerial, but many times you first ran forward and hopped back in order to do so. The running forward wastes time, provides a small amount of vulnerability that can easily be picked up on, and (against the higher tier characters or against characters with more speed/priority/range) can just end up getting you dominated.
^ this paragraph about Fair is only my opinion, but in my usage of Fair, I haven't gotten much out of it... when i used to spam it as such, it just got me killed, and because of that I would like to warn you of that. Fair is a good move when used in moderation. Mindless spamming will put you into a bad situation eventually. (I could tell your intention by retreating the fairs that you used, but nair, bair, uair, DTILT, FTILT, and several other attacks will rack up damage in a much better way than fair will [against the better of players], IMO of course. None of this is 100%, because I haven't really played brawl in about a month.... XD)
All of ness' attacks are great to use in almost any type of situation. I took one match of yours and approximated the usage of every move:
Moves are given a percentage usage, ranging between values because I don't know the exact number.
Aerials: 50-70%
--(percentage Aerial subcategory)
--Fair: 60-80%
--Bair: 20-35%
--Nair: 15-25%
--Dair: 5-15%
--Uair: 5-10%
Ground: 5-10%
--Usmash: 10-50%
--Fsmash: 30-65%
--Jab: 20-35%
--Other: 5-10% (I'm not too sure... it may actually be 0%, since you used so few grounded attacks other than pkfire)
Grabs (yes, separate from ground): 10-30%
--SIDENOTE: many of the grab attempts were thrown out without connecting. Of the ones that landed...
--Fthrow: 25-60%
--Bthrow: 10-25% (used as it should be, mostly for killing)
--Uthrow: 15-25%
--Dthrow: ??? (don't remember seeing it in the match that I looked at... I watched a lot of them, but I used one to approximate the usage of moves)
Specials: 15-25%
--Pkfire: 50-70% (saw lots of spamming)
--PkT: (away from recovery
10-20%
--PkFlash: 0%
--PSI Mag: 5-10% (
)
Now looking at that, I see some things wrong.... As stated before, Fair is in significant usage, as well as PKFire... I also noted that there were few, if any, attempts at throwing in ftilt, dtilt, utilt, which are all moves that can be used well in many cases (dtilt, if spaced properly, trips nearly 100% of the time; ftilt can push ppl back if thrown out at proper times; utilt is quick, juggles, kills quicker than usmash, and somewhat easy to land if you're used to it). What I also wanted to see was MOAR PSI MAGNET!!! (As I tell absolutely everyone by now...) Magnet is much more useful than anyone knows... especially in B+... Magnet was crap in 64 and melee, but Brawl it can at least serve some purpose other than absorption. Also, WHERE IS THE PKFLASH?!?!?!? Okay, sure, I was watching a lucas match and it wouldn't make much sense to give your opponent free damage recovery, but you can throw it in there once in a while if placed smartly. Did you know that PKFlash uncharged could potentially lead into nair or uair if started when ness is a slight distance above the ground? I use it on my friends all the time, and they find it extremely difficult to avoid the oncoming aerial...
Now overall, the spread between all the types of attacks should be about even, with grabs slightly less... lets say about 37/23/15/25 just for the sake of putting numbers into this. I'll explain what I mean by this.
Since ness is supposed to be really good in the air, it only makes sense to use his aerial moves the most. but by doing that ALL the time, you become easy to read, counter, and defend against, because all of his aerials can be destroyed if the opponent knows what to do. Ground attacks, IMO, are severely under-rated for ness. His tilts all provide some significant boost to his game, while his smashes are good enough to punish. Jabs, IMO, are terrible. Anyone, with good timing, can either shield the third hit in ness' jab combo or out-speed him when ness tries to jab into something else. Because of this, I use dtilt lots more. it's quick, provides several setups into things, can trip, and allows for you to react if needed. Moving on to grabs, I highly recommend only using the grabs if you know you will grab. Many people I see often dashgrab and overshoot the opponent, leaving them in a world of hurt. only grab when the opportunity is right and you are within the proper range/spacing for grabbing. Now with throws, Bthrow is what you used well: keep using it only near the killing % range. Bthrow = Killer... people fear it. Fthrow and Uthrow do more damage than Dthrow, but Dthrow can lead into some pseudo combos on people. I recommend using fthrow the most, uthrow slightly less, and dthrow the least, mostly only if you use pkfire > grab.... (looks cool!). With special techniques, PKFire is somewhat good, but many people know how to properly SDI out in offline games. I like PKfire, but I tend to avoid grounded. I instead use PKFire when I FH, which (if done properly) allows me to do an aerial, airdodge, jump back, do lots of things... grounded is much more difficult to hit with, because all your opponent needs to do is jump and approach and you are on the defensive. The FH version keeps you a little less approachable, but only if you space it right. PSI Magnet is good as I said before, Pkflash is good for mindgames and uber rare combos... PKT is good overall. PKT mindgames are fun to do. Because it is easy to control, you can do lots to mind**** everyone, and even PKT2 in some cases to either retreat, attack based on an opening produced by pkt mindgames, or just random stuff....
Sorry if I seemed to rant, but I like to give constructive criticism... if you have questions, ask.... I'm happy to help anyone who wants my help... XD (I'm no pro like vice, shaky, or smash64, but I know quite a bit)